This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This program aims to determine the structures of proteins involved in cell membrane targeting, adhesion, and signaling, in order to establish the mechanism and specificity of their interactions. There are currently two projects with crystals that require synchrotron radiation. 1. Structure of full-length a-catenin, an F-actin binding protein that couples cadherin-based cell adhesion to regulation of the actin cytoskeleton. 2. Complexes of the SNARE regulator Munc18a bound to mutants of the SNARE syntaxin that will allow understanding of allosteric regulation of this interaction.